1. Field of the Invention
The present invention relates to a wooden structure in panel form which is manufactured from thinned lumber, particularly to a wooden structure in a panel form manufactured by utilizing thinnings.
2. Description of the Related Art
Thinned logs are lumber that is cut from an afforested area. The thinned logs typically have small annual rings and are predominately immature wood. As a result, their usefulness is limited due to their shape and quality. Attempts have been made, however, to use the thinned logs for sound insulating walls.
A sound insulating wall is constructed, for example, by the following procedure: logs from thinning are cut to have a given length; the opposing two sides are cut along the length of the thinned logs parallel to each other so as to form columns each having two parallel flat surfaces; the columns are arranged in parallel in such a manner that one flat surface of one of any two adjacent columns is contacted with a flat surface of the other one of the two columns; bolts are passed through respective penetrations provided in the columns and then sequentially clamped to give a panel; the panels thus obtained are allowed to stand continuously and vertically in a wall form (Japanese Unexamined Patent Publication Nos. 5-141022 and 7-305413).
However, since the sound insulating wall prepared by using logs from thinning is made of wood, the wall dries and shrinks in the winter, forming gaps between the columns. As a result, noise leaks through the gaps, and the sound insulating wall functions poorly as noise insulation. When the clamping force of the bolts is strengthened to overcome this disadvantage, the columns themselves are damaged and the durability of the sound insulating wall is significantly impaired.
On the other hand, an arrangement of coil springs between the panels and the respective bolts have been proposed. In this case, the elongation and shrinkage of the columns are absorbed by the elastic force of the coil springs. When the coil springs are used, the number of parts is consequently increased. This results in the assembly of the panel becoming very complicated with an increase in the production costs (Japanese Unexamined Patent Publication Nos. 6-200571 and 7-71080)